Overview
Attila is a feral steppe world whose clans measure worth in horses, raids, and the quality of their enemies.
The Imperium harvests its riders as scouts and shock cavalry, exporting a way of war older than voidflight.
Beyond the Rift, its musters continue whether or not anyone arrives to collect them.
M41 and M42 status
Feral world of horse-clans and rough riders.
Nihilus-side feral world; tithes ride out into the dark.
Timeline
Rough rider regiments enter wide Imperial service.
Clan confederations formalise tithe musters under Munitorum seal.
The Rift strands Attila on the dark side of the wound.
Sporadic contact confirms the clans still ride and still fight.
Cartographic positions and several administrative details are intentionally approximate where published Warhammer sources conflict or provide no canonical coordinate system.